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In a programming language, an evaluation strategy is a set of rules for evaluating expressions. [1] The term is often used to refer to the more specific notion of a parameter-passing strategy [2] that defines the kind of value that is passed to the function for each parameter (the binding strategy) [3] and whether to evaluate the parameters of a function call, and if so in what order (the ...
Values of reference type refer to objects allocated in the heap, whereas values of value type are contained either on the call stack (in the case of local variables and function parameters) or inside their containing entities (in the case of fields of objects and array elements). (With reference types, it is only the reference itself that is ...
In case of call by value, what is passed to the function is the value of the argument – for example, f(2) and a = 2; f(a) are equivalent calls – while in call by reference, with a variable as argument, what is passed is a reference to that variable - even though the syntax for the function call could stay the same. [5]
[16] [17] And with certain programs the number of steps may be much smaller, for example a specific family of lambda terms using Church numerals take an infinite amount of steps with call-by-value (i.e. never complete), an exponential number of steps with call-by-name, but only a polynomial number with call-by-need.
For example, in assignment a = b the target a is not evaluated, but instead its location (address) is used to store the value of b – corresponding to call-by-reference semantics. Further, an assignment may be a statement (no value), or may be an expression (value), with the value itself either an r-value (just a value) or an l-value (able to ...
The return value (or a pointer to it) is returned in a register. Some conventions use registers for the first few parameters which may improve performance, especially for short and simple leaf-routines very frequently invoked (i.e. routines that do not call other routines). Example call:
Specify a return value in the function body; Call a function; Provide actual parameters that correspond to a called function's formal parameters; Return control to the caller at the point of call; Consume the return value in the caller; Dispose of the values returned by a call; Provide a private naming scope for variables
In programming language theory, call-by-push-value (CBPV) is an intermediate language that embeds the call-by-value (CBV) and call-by-name (CBN) evaluation strategies. CBPV is structured as a polarized λ-calculus with two main types, "values" (+) and "computations" (-). [ 1 ]